Coins don't aggregate automatically, but if you send a transaction bigger than any of the individual "coins" in your wallet, the transaction will effectively combine enough of your coins to cover the transaction, the result being an aggregate "coin" whose value is the sum of all the inputs. The only way to get a bunch of 0.0001's in your wallet is to receive many transactions of that size and then, importantly, to never send any of them out. If your wallet only contains 0.0001's and you do a single send transaction, the ones you send will combine.

Companies claiming they got hacked and lost your coins sounds like fraud so perfect it could be called fashionable. I never believe them. If I ever experience the misfortune of a real intrusion, I declare I have been honest about the way I have managed the keys in Casascius Coins. I maintain no ability to recover or reproduce the keys, not even under limitless duress or total intrusion. Remember that trusting strangers with your coins without any recourse is, as a matter of principle, not a best practice. Don't keep coins online. Use paper wallets instead.

So yes, Bitcoin will group up the coins with time. Sometimes Bitcoin will have many change addresses and for those to be combined you have to spend an amount bigger than the change addresses. So if you spent all your BTC back to yourself it will combine all your coins. Not really worth it though as it doesn't really accomplish much and you may end up paying fees depending on how many small amounts you have.

SO i could just send the bitcoins to myself and that would defrag my bitcoins as well?

It would, but the way the current software works, it doesn't delete old transactions. So while yes they would be defragmented, every node on the entire network would also have the old fragmented copy as well.

I will bet soon enough there will be a client that can ignore or discard old transactions, because the growth of the block chain and every user having to download it is going to be unsustainable. But for now, it will have no practical benefit.

Companies claiming they got hacked and lost your coins sounds like fraud so perfect it could be called fashionable. I never believe them. If I ever experience the misfortune of a real intrusion, I declare I have been honest about the way I have managed the keys in Casascius Coins. I maintain no ability to recover or reproduce the keys, not even under limitless duress or total intrusion. Remember that trusting strangers with your coins without any recourse is, as a matter of principle, not a best practice. Don't keep coins online. Use paper wallets instead.